Re: surface/volume ratio and water loss in smallest amniotes

[Dann Pigdon <dannj@alphalink.com.au>]

On Thu, Feb 11th, 2010 at 2:54 AM, David Peters <davidpeters@att.net> wrote:

> Question is: Whether or not the smallest pterosaurs were adults or
> hatchlings, if they were in the airstream, were they evaporating at a
> dangerous rate?

Maybe if they had highly permeable skin like that of amphibians, or even porous 
glandular skin 
with sweat glands like some mammals. Having membaneous wings would probably 
negate the 
need to sweat to keep cool though.

Perhaps the apparent lower size limit for flying vertebrates has more to do 
with heat retention than 
evaporation? Small creatures with wings might be more prone to heat loss in 
cool conditions, if 
having wings drastically increases their surface area to volume ratio (which I 
suspect would be the 
case - especially with membraneous wings). All flying vertebrates appear to 
have been 
endotherms, if pterosaur integument is anything to go by, so avoiding 
catastrophic heat loss might 
be a limiting factor for minimum size.

-- 
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Dann Pigdon
GIS Specialist                         Australian Dinosaurs
Melbourne, Australia               http://home.alphalink.com.au/~dannj
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